This application claims the priority of German Patent Application Serial No. 198 34 513.5, filed Jul. 31, 1998, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to tripod type constant-velocity universal joint.
Typically, a constant-velocity universal joint of a tripod type has a housing as first rotation part which is provided with three tracks, each including two running surfaces in parallel relationship, and a second rotation part in the form of a tripod spider. The second rotation part includes three arms defining axes arranged in a plane and intersecting in a joint axis. The arms are guided by rolling-contact bearings in the running surfaces of the tracks for angular movement and displacement. Each arm is assigned to a rolling-contact bearing which includes an inner ring and outer ring for guiding cylindrically shaped rolling elements therebetween. A mutual securement of the components and a captivated unitary structure of the rolling-contact bearing are implemented by providing retainer rings.
Constant-velocity universal joint of the tripod type is oftentimes used in driveshafts of driven front wheels of motor vehicles. A typical example of a tripod joint is disclosed in German Pat. No. 43 31 474 and includes a rolling-contact bearing provided with an axial securement for all components thereof. In one variation, the rolling-contact bearing has an outer ring of asymmetric configuration with one-sided collar as axial stop for the rolling elements. Axially offset to the axial stop for the rolling elements, the radially inwardly directed collar is formed with an annular groove for placement of a retainer ring. On the inside, the retainer ring is fixed in a circumferential groove formed in the inner ring of the rolling-contact bearing and aligned with the radial groove. A further axial stop for the rolling elements is effected by providing the outer ring with a securing ring which is placed in an annular groove of the outer ring and extends on the inside toward the peripheral surface of the inner ring of the rolling-contact bearing while maintaining on the inside an annular gap. This conventional configuration of the rolling-contact bearing requires a precise positional assembly as a consequence of the asymmetric configuration of the outer ring.
German Pat. No. 44 29 479 C2 discloses a tripod-type constant-velocity universal joint in which a mutual, axial securement of all components of the rolling-contact bearing, arranged on arms, is realized by providing retainer rings which are placed in annular grooves of the outer rings of the rolling-contact bearing. Each of these retainer rings has on the outside the outer contour of the inner ring, whereby the retainer rings provide an axial stop for the rolling elements as well as for the inner ring, with these components directly supported upon the retainer ring. As a consequence of the common support upon the retainer ring, the latter is exposed to a higher transverse force and requires stronger dimensioning. A respectively reinforced and thus stiff retainer ring adversely affects, however, handling.
It would therefore be desirable and advantageous to provide an improved constant-velocity universal joint of the tripod type, which obviates prior art shortcomings and effects an axial securement for all components of the rolling-contact bearing, while yet allowing simple handling and cost-efficient fabrication of retainer rings.
The present invention provides for a constant-velocity universal joint of a tripod type, which includes a housing representing a first rotation part and having three tracks, each track having two flat running surfaces in parallel relationship, a second rotation part configured as a tripod spider and having three arms defined by arm axes arranged in a plane and intersecting in a joint axis, wherein the arms are guided in the running surfaces of the housing, with each of the arms received in a rolling-contact bearing including an inner ring, an outer ring, cylindrical rolling elements, and retainer rings arranged as mirror images of one another for mutual axial securement of all components of the rolling-contact bearing with respect to the arm axis, wherein the outer ring includes inner collars which are arranged as mirror images of one another, each inner collar configured with two radial steps to define an axially inner collar segment and an axially outer collar segment, with the rolling elements guided on the inner collar segment and with the retainer rings guided on the outer collar segment.
The novel and inventive configuration according to the present invention results in a desired, separate axial guidance between the rolling elements and the retainer rings, so that these components are prevented from influencing each other, i.e. the inner collar segment of the outer ring, forming an axial stop, and the retainer rings absorb only transverse forces from the component that is associated thereto. Thus, the retainer rings can be of lighter configuration as prior art constructions, i.e. the required wall width of the retainer rings can be reduced. Moreover, the retainer rings may have a smaller diameter as they do not overlap the structural height of the rolling elements but are guided at the radially inwardly offset step of the outer ring. The retainer rings can thus be manufactured at lower costs and can be better handled as the decreased stiffness facilitates the assembly.
In accordance with the present invention, the axial guidance for the rolling elements and the axial guidance for the inner ring of the rolling-contact bearing are clearly separated from one another. At the same time, a simplified assembly of the retainer rings is established which have smaller dimensions, i.e. a smaller outer diameter, as well as reduced wall width. In addition, the novel and inventive rolling-contact bearing allows the use of rolling elements of a width which is the same as in prior art constructions.
According to another feature of the present invention, the axial distance between the first radial step and the second radial step is so selected as to exceed the wall width of the retainer rings. This stepped configuration allows the use of an inner ring of a width which exceeds a length of the rolling elements, thereby ensuring that the rolling elements are supported and guided over the entire length on the outer surface of the inner ring.
A simplified installation of the retainer rings in the outer ring of the rolling-contact bearing is implemented when providing the retainer rings with a parting line. Hereby, the parting line can have a width which is independent from the diameter of the rolling elements. A great line width considerably simplifies the installation as a result of the simplification of the required radial compression of the retainer rings during installation, so that handling and installation of the retainer rings are improved. As the retainer rings are provided solely for support and guidance of the inner ring of the rolling-contact bearing, the width of the parting line can be dimensioned solely on considerations of simplifying the installation. Unlike in conventional constructions, there is no need to suit the width of the parting line of the retainer rings to the diameter of the rolling elements. As a consequence, there is no need for a preferred disposition of the parting line, i.e. the parting line may be formed radially in the retainer ring or oblique with respect to a radial extension.
Suitably, the outer ring of the rolling-contact bearing is provided in immediate proximity of the area of the first radial step, i.e. at the end of the track for the rolling elements, with a circumferential undercut for providing a relief, i.e. prevention of stress peaks introduced by the ends of the rolling elements into the tracks of the outer rings. The undercut is so positioned and configured as to correspond with the free end of the rolling element.
To effect a certain degree of freedom, the retainer rings are installed at a distance to the confronting end faces of the inner ring. This axial play enables an alignment between the components of the rolling-contact bearing at installation and prevents disadvantageous warping.
It may also be suitable to provide an overlap between the inner diameter of the retainer rings and the outer diameter of the inner ring, whereby a sufficient positional securement of the inner ring is established when the overlap is dimensioned to correspond to or exceed half a wall width of the retainer rings.
The axial outer collar segment of the outer ring of the rolling-contact bearing may be configured to correspond to or exceed half a wall width of the retainer rings.
According to another feature of the present invention, the outer ring of the rolling-contact bearing may have different outer profile. For example, the outer ring may have a rounded, substantially semicircular outer profile. It may also be possible to configure the outer ring with a cylindrical outer profile with a radially stepped, cylindrical portion, whereby the radially projecting cylindrical portion may be disposed in symmetry or optionally in offset relationship to the center of the outer ring. Another construction of the outer ring may include a configuration resembling a pointed roof.